Add async/Collect
SearchPage: Synchronize loading of tweets and users
ProfilePage: Use a GSimpleAction to (un)block

... which makes it possible to disable it for the authenticating
account.
ProfilePage; Use block_item_blocked in a different way

It used to prevent the callback from being called when we set the
GtkMenuItem's state manually but that's not the case anymore and we can
just use it to prevent people from clicking it multiple times.
ProfilePage: Disable the blocking action

... if the profile's user is the currently logged-in user.
ProfilePage: Add retweet disabling/enabling
Twitter: Catch errors when loading avatars
ProfilePage: Show tweets again after following a user...

... you have just unfollowed.
Show/hide retweets when enabling/disabling retweets
Twitter: Return no_avatar if avatar could not be loaded

This can e.g. happen if an avatar is not a valid png/jpg file.
Twitter: Don't check if the file exists before reading it
Utils: Print line/file in show_error_object
filter-page: Add some space to the Users label
UserLists:widget: Don't show the "created" label for the user
tweet-info-page: remove xalign from name_button
Update PO files
AccountDialog: Fix overlapping widgets
ListUserEntry: Fix spacing
dm-placeholder-box: Refine spacing a bit
Merge branch 'master' of https://github.com/baedert/corebird